Method and device for a real time measurement of output torque of an automobile engine

ABSTRACT

This invention is a device for real-time measurement of torque output from an automobile engine. The device measures the deformation of damper springs of a planar clutch plate and interprets the deformation as the output torque while the automobile is in operation. The device is comprised of (i) a planar disc clutch plate which includes damper springs, (ii) first and second sets of posts which are welded onto the clutch plate, (iii) a signal pick-up sensor and (iv) an electronic circuit to process the picked-up signals.

TECHNICAL FIELD

The present invention generally relates to a real time measurement oftorque output from an engine to a transmission of an automobile, andmore particularly to a device and a method for real time measurement oftorque output from an engine to a transmission having a plate typeclutch by means of the interaction of a clutch plate and damper springsof the clutch.

BACKGROUND ART

One of the most important goals in engine development is to maximizeoutput power while minimizing fuel consumption. To assess this goal, themeasurement of engine output torque is essential. Yet currentlyavailable technologies measure the revolution speed (rpm) of the engineand not the output torque while the engine is running. Power is, bydefinition, torque multiplied by the angular velocity. At present,torque measurement requires special equipment and set up.

There are basically two ways of torque measurements. The most commonmethod is to acquire torque by separately measuring power and angularvelocity and subsequently dividing the power by the angular velocity.The other method is to acquire torque by measuring minute twists of theclutch axle of a power train by means of a strain gauge attached to asurface of the clutch axle and detecting signals indicating the measuredtwist through slip rings incorporated onto the clutch axle. Both of theabove methods are applicable only when the engine is tested on a testbench, but not when the engine is mounted on an automobile.

A recently reported new technology makes use of magneto-elasticity ofcertain materials. This technology is also based on the measurement ofminute twists of the clutch axle, yet it is applicable for real-timemeasurements during the operation of an engine. The measurement of themagneto-elasticity involves some modification of the clutch axle of thepower train.

DISCLOSURE OF INVENTION

Therefore, this invention is intended to solve the problems of the priorart torque measurements. This invention provides a device and a methodfor real time measurement of instantaneous torque output from anautomobile engine while the engine is mounted on the automobile andrunning.

According to the invention, there is provided a device for real timemeasurement of torque output from an engine to a transmission of anautomobile comprising a plate type clutch with a clutch plate forintermitting the engine power, a clutch shaft for connecting the clutchplate to a transmission, and an axle guide tube for surrounding theclutch shaft over a length of the clutch shaft. The clutch platecomprises a lower body member with annular frictional materials attachedalong peripheries on both sides thereof and formed with a first apertureat a central portion thereof, an intermediate body member with a hubpenetrated into and attached to the intermediate body member at acentral portion thereof, and an upper body member formed with a secondaperture at a central portion thereof and adapted to be positioned ontothe intermediate body member. The hub is adapted for coupling with theclutch shaft. A lower portion of the hub is inserted into the firstaperture and an upper portion of the hub is inserted into the secondaperture. The intermediate body member is adapted to be positioned ontothe lower body member. The lower and upper body members are fixedlyfastened together with the intermediate body member interposedtherebetween to be circumferentially displaced relative to the lower andupper body members by a damper spring means. The device includessignal-producing reference means formed on the clutch plate, at leastone sensor mounted into a mounting aperture in a leading end portion ofthe axle guide tube to be positioned radially inside thesignal-producing reference means and to face the signal-producingreference means, and computing means for receiving a signal output fromthe sensor and for computing the engine torque based on the signal. Thesignal-producing reference means includes a first plurality of axiallyextending posts formed equidistantly around a periphery of the upperportion of the hub, and a second plurality of axially extending postsformed equidistantly around a circumference of the second aperture ofthe upper body member. The first posts are disposed radially inside thesecond posts.

The invention accomplishes the torque measurement by sensing thedeformation of the damper spring means. When the automobile enginedelivers torque to the transmission, the torque is relayed by the damperspring means. The spring means are compressed proportionally to thetorque which the spring means relays to the transmission. The degree ofcompression of the damper spring means is non-contactively measured andthe measured data is transmitted from the interior of the clutch to theexterior computing means while the clutch plate is rotating togetherwith the engine output shaft.

The precise measurement of instantaneous torque enables one tofacilitate a feed-back control in the engine control unit. Instantaneoustorque measurement may provide information on the state of the engine aswell.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partially sectioned, schematic side view of a clutchincorporating a portion of a device for real time measurement of torqueoutput from an engine according to the present invention.

FIG. 2 is an exploded perspective view of a clutch plate with respectiveposts formed on an upper body member and a hub of the clutch plate,respectively.

FIG. 3 is a sectional view showing the assembled state of the clutchplate shown in FIG. 2.

FIG. 4 is a partially cut-away plan view of the clutch plate when notorque is applied.

FIG. 5 is a partially cut-away plan view of the clutch plate similar toFIG. 4 but when torque is applied.

FIG. 6 is a longitudinally sectioned fragmentary view showing a damperspring inserted into the clutch plate.

FIG. 7 is a perspective view of an axle guide tube and a pickup sensoradapted for installation to the axle guide tube.

FIG. 8 is a partially cut-away, sectioned side view of the axle guidetube when assembled.

FIG. 9 depicts output signals from the pickup sensor, wherein (a) is adiagram when applied torque is zero and (b) is a diagram when appliedtorque is non-zero.

FIG. 10 is a graph showing one example of relative torque measured andcomputed by the present invention, with regard to crank angles of theengine.

MODE FOR CARRYING OUT THE INVENTION

FIG. 1 shows a clutch incorporating a portion of the device for realtime measurement of torque output from an engine according to thepresent invention.

A clutch plate 1 of the clutch, which relays the rotational power of anengine shaft 2 to a clutch shaft 7 for connecting the clutch plate to atransmission, is located between a flywheel 3 and a pressure plate 4.When urged by the pressure plate 4, the clutch plate 1 is pressedagainst the flywheel 3 and the clutch plate 1 rotates with the flywheel.Therefore, the clutch shaft 7 spline-coupled to the clutch plate 1 via ahub rotates with the clutch plate 1. When the pressure plate 4 isretracted to relieve the pressure, the clutch plate together with theclutch shaft does not receive rotational power from the engine.

Referring to FIGS. 2 and 3, the clutch plate 1 includes a lower bodymember or base plate 10, an intermediate body member or teeth body 20,and an upper body member or top plate 30. The base plate 10 has annularfrictional materials 13 attached along peripheries on opposed sides andis formed with a first aperture at a central portion. The teeth body 20has a hub penetrated into and attached to the teeth body at a centralportion. The top plate 30 is formed with a second aperture at a centralportion and adapted to be positioned onto the teeth body. The hub isadapted for the spline coupling with the clutch shaft 7. A lower portionof the hub is inserted into the first aperture and an upper portion ofthe hub is inserted into the second aperture. Rivets 33 fasten the topplate 30 and the base plate 10 through rivet holes 11 and 31 therein.The teeth body is kept between the two plates, but is rotatable by asmall angle between the adjacent rivets. Each of spring wells 12, 32 and21 in the respective plates and teeth body is aligned together andcaptures a damper spring 23 therein. When the pressure plate 4 urges theclutch plate 1 towards the flywheel 3, the rotational power of theengine is delivered to the base plate 10 of the clutch plate 1 with thefriction coupling between the friction materials 13 of the opposedsurfaces of the base plate 10 and the flywheel 3 and the pressure plate4. The rotational power delivered to the base plate 10 acts on andcompresses the damper springs 23. The damper springs 23 in turn deliverthe rotational power to the teeth body 20. The teeth body 20 turns theclutch shaft 7 with the spline coupling between the hub at the center ofthe teeth body 20 and the clutch shaft 7. This configuration permits thetransfer of the engine power to the clutch shaft 7 through thecompression of the damper springs 23 as relaying members.

To achieve the real time measurement of torque output from the engineaccording to the invention, two augmentations are incorporated assignal-producing reference means into the clutch plate 1. Theaugmentations are a first plurality of axially extending posts 22 formedequidistantly around the periphery of the upper portion of the hub and asecond plurality of axially extending posts 34 formed equidistantlyaround a circumference of the second aperture of the top plate 30, asshown in FIGS. 2 and 3. In FIG. 2, six of the first posts 22 are weldedon the hub of the teeth body 20 and six of second posts 34 are disposedon the top plate 30. FIG. 4 shows the relative positioning of the firstand second posts in the assembled clutch plate. The first posts 22 aredisposed radially inside the second posts 34. Preferably, each of thefirst posts is located equiangularly relative to circumferentiallyadjacent two second posts. The exact number of first and second postsrequired can be varied depending on specific design needs.

FIG. 5 shows the first posts on the hub of the teeth body slightlydisplaced circumferentially from their original positions relative tothe second posts, and FIG. 6 is a longitudinally sectioned fragmentaryview showing the damper spring inserted into the clutch plate. The stateshown in FIG. 5 occurs when the damper springs are forcibly compresseddue to the torque or power relayed by the damper springs from the engineto the clutch shaft. The arrow in FIG. 6 indicates the direction ofcompression of the damper spring. The measurement of torque isaccomplished by detecting an angular displacement of these posts andtransmitting the detected signals indicating the angular displacementinto a computing means external to the clutch assembly.

FIG. 7 is a perspective view of an axle guide tube 8 and a pickup sensor40 to be installed in the axle guide tube. The axle guide tube 8surrounds the clutch shaft 7 over a length of the clutch shaft.According to the invention, the axle guide tube 8 is slightly modifiedto have a sensor mounting aperture 42 at the leading end portion thereofand a wire trough 43 which is contiguous to the sensor mounting apertureand extends at a predetermined length over the length of the axle guidetube. The pickup sensor 40 is installed in the sensor mounting aperture42. When finally assembled with the clutch plate, the pickup sensor 40is positioned radially inside the first and second posts and faces them.Lead wires 41, preferably a pair of wires, from the pickup sensor arefitted into and brought out through the wire through. The wires 41transmit signals output from the pickup sensor to the computing means.For certain applications, more than one pickup sensor may be needed andthe number of the sensor mounting apertures and the wire troughs mayincrease with the number of the pickup sensors.

Referring to FIG. 8, the axle guide tube 8 in which the pickup sensor 40is installed is fixedly bolted inside a clutch housing 6 which has beenpreviously bolted in place, and the clutch shaft 7 passes through theinside of the axle guide tube 8. The clutch shaft 7 is spline-coupledwith the hub of the clutch plate 1 (not shown in FIG. 8) and rotateswith the clutch plate 1.

In operation, the first and second posts 22 and 34 rotate with theclutch plate 1 and pass over the bottom surface of the pickup sensor 40.When the posts pass over the bottom surface of the pickup sensor 40,signals as shown in FIG. 9 are produced. The taller pulses representsignals indicating the passage of the first posts 22 which are closer tothe bottom surface of the pickup sensor, and the smaller pulsesrepresent signals indicating the passage of the second posts. The timeintervals of the signals produced from the pickup sensor when posts passover the sensor are measured. When no torque is applied, the signals asshown in FIG. 9(a) are produced from the pickup sensor. When non-zerotorque is applied, the signals as shown in FIG. 9(b) are produced fromthe pickup sensor. The displacement of the smaller pulses in the FIG.9(b) increases proportionally with the increase of the applied torque.The measured time intervals of the signals which are proportional to theangular relative displacement of the posts can be converted to torquevalues by appropriate conversion formula previously stored in thecomputing means.

Although one pickup sensor is used in this embodiment, a plurality ofpickup sensors 40 may be used such that they are placed around thecircumference of the axle guide tube 8. With one pickup sensor, thenumber of data acquisition per one revolution of the engine is limitedto the pair numbers of the first and second posts 22 and 34. With sixpairs of the first and second posts 22 and 34 as shown in FIGS. 4 and 5,six data points are acquired for each revolution of the engine, or onedata point for every 60 degrees of turn. If the number of the pickupsensors 40 is increased to 4, then data will be available for every 15degrees of turn.

FIG. 10 shows simulated output torque variations as a function of thecrank angle of a 4-stroke, 4-cylinder engine. Reference character A inFIG. 10 represents torque variations for an ideal case, and referencecharacter B represents a torque variation when the number two cylinderwas partially misfiring. The data points were acquired for every 15degrees of turn. FIG. 10 shows that real time instantaneous detection oftorque output from an engine can be used to diagnose engine performanceand even identify the specific cylinder that is misfiring.

Although the device of the invention has been described and illustratedfor a specific embodiment, the invention is not intended to be limitedto the embodiment and may be greatly varied especially with regard toconstruction without departing from the guiding principles disclosedabove and claimed below. For example, by appropriately selectingmaterials and configurations for the posts, other desired signal formsmay be obtained.

Industrial Applicability

The output power of an automobile engine is a function of manyparameters such as, amount of intake air, air-fuel ratio, ignitiontiming, road condition (load), and the like. The existing technologywhich measures the rotational speed and the above parameters, controlsthe engine by a heuristic approach. There is a need to improve the priorart technology. By being able to measure the output torqueinstantaneously according to the present invention, a feedback controlcan be applied to achieve the best performance for an engine. Further,the device of the invention is readily adaptable to a conventionalclutch system with minimal modification, and its assembly to anddisassembly from the clutch system can be effectuated with ease.

What is claimed is:
 1. A device for real time measurement of torqueoutput from an engine to a transmission of an automobile comprising: aplate type clutch with a clutch plate for intermitting the engine power;a clutch shaft for connecting said clutch plate to a transmission; anaxle guide tube for surrounding said clutch shaft over a length of saidclutch shaft, wherein said clutch plate includes a lower body memberwith annular frictional materials attached along peripheries on bothsides thereof and formed with a first aperture at a central portionthereof, and an intermediate body member with a hub penetrated into andattached to said intermediate body member at a central portion thereof,said hub being adapted for coupling with said clutch shaft and a lowerportion of said hub being inserted into said first aperture, saidintermediate body member being adapted to be positioned onto said lowerbody member, and an upper body member formed with a second aperture at acentral portion thereof and adapted to be positioned onto saidintermediate body member, an upper portion of said hub being insertedinto said second aperture, said lower and upper body members beingfixedly fastened together with said intermediate body member interposedtherebetween to be circumferentially displaced relative to said lowerand upper body members by a damper spring means; a signal-producingreference means formed on said clutch plate, wherein saidsignal-producing reference means includes a first plurality of axiallyextending posts formed equidistantly around a periphery of said upperportion of said hub, and a second plurality of axially extending postsformed equidistantly around a circumference of said second aperture ofsaid upper body member, said first posts being disposed radially insidesaid second posts; at least one sensor mounted into a mounting aperturein a leading end portion of said axle guide tube to be positionedradially inside said signal-producing reference means and to face saidsignal-producing reference means; and computing means for receiving asignal output from said at least one sensor and for computing the enginetorque based on said signal.
 2. The device of claim 1, wherein said axleguide tube comprises a trough which is contiguous to said sensormounting aperture and extends a predetermined length over the length ofsaid axle guide tube, and wherein a pair of wires for transmitting saidsignal output from said sensor to said computing means is fitted intosaid trough.
 3. The device of claim 1, wherein each of said firstplurality of axially extending posts is located equiangularly relativeto two circumferentially adjacent posts of said second plurality ofaxially extending posts.